Merger Accounting - Preliminary Purchase Price Paid (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Mar. 13, 2019	Mar. 12, 2019	Dec. 31, 2019
Business Acquisition [Line Items]
Fair value of consideration issued it effect the Merger			$ 45,541
Arsanis
Business Acquisition [Line Items]
Number of shares of the combined organization owned by Arsanis stockholders (in shares)	2,440,582
Multiplied by the fair value per share of Arsanis common stock (in dollars per share)	$ 18.66
Fair value of consideration issued it effect the Merger	$ 45,541
Fair value of replacement awards held by former employees, board of directors and consultants of Arsanis that were vested as of the Merger.	817
Purchase price	$ 46,358
Common stock outstanding (in shares)		14,643,737